Compressor



Patented July 2, 1935 0.

' UNIT-ED ST TES; OFFICE COIWIPRESSOR French ,E. Dennison, York; Pa., assignor to York Ice Machinery Corporation, York, PaL, a cor- Duration of Delaware Application March;19 1934; Serial no. 716,383 10 claims,- (01, 2s0-i90) -;-This;invention relates to compressors, andparhand,- when t mpr is at rest, l ilm" ticularly to means for unloadingthe compressor is not maintained. So that the ports re when at rest, without involving material slip or free of oil and-serve to unload the compressor at leakage while the compressor is in operation. a rate sufficiently rapid to ensure unloading by The principal advantage of the unloading the time the compressor is restarted. l 2.

. :53 means disclosed, is the fact that it involves no Other factorswhich assist in precluding back moving parts, and thus accomplishes the desired. flow-through the unloading p are the rather result in the simplest possible manner. 7 high piston speed and the arrangement of the Theinvention is intended chiefly for use in port at a right n le to h p h f ecipro a ion 10, small refrigerating units of the compressor, conof the piston, a d t Cylinder a There is 102 denser, evaporator circuit type, but is available What maybe described as a labyrinth e and for usein other situations. this is particularly pronounced at high piston If the compressor stops, with the piston on the sp I f 1 compression stroke, or if there is slight leakage The preferred embodiment of the invention asfrom the discharge of the compressor throughthe applied. to an air-cooled comp of a yp ve 1 5 .1

discharge valve'to the cylinder, the starting load tensivelyused refrigerating-units, will now be on the motor whicndrives the compressor will described in connection with the accomp y be considerable, and to meet this conditionit has g, in. which the single fi r is a Verticalheretofore been the practice to use a. motor. with axial se on of o cylinder of a multi-cylinder a high starting torque which entails the uselof mpressor with the inv n i n applied. 20;

an: unnecessarily large and heavymotor, or else In the draw i p t e. Cy W to provide some automatic unloading means provided with coolingv fins 6. The upp end of which opens an unloading port h th the cylinder is closed by a head 1 having dispressor comes to rest. The latter expedient in har e ports .8 arran e 1 1 a circ l r ri s c m volves the use of rather sensitive and expensive. i With th y clamped to the G 25. mechanism and does not protect the motor from terof t h ad y me s o a bol 9, nut:-ll overload in the event that the unloading mechaand locknut this a flexible disk valve I3; which nism fails to function. Most known unloading. coacts withannular seat ribs n I5 b mechanisms. are subject to occasional 'failuresto tween .Whichthe p 8 a e c sk 30.; function. I3 is ported, as indicated at I6, and controls flow.

- The present invention involves theme of a to o e P e l1 Whichis ncl d by a bleedport which becomes effective tounload the housing The housing is s p ovid d W compressor when the compressor stops and which toolingv fi and held to yl d l' Castis. sealed against leakage when the compressor is insb h n s ws w c pass t h a in motion. Generally stated, the invention onflange-on the housing l8 and through the head 35;. templates the use of one or more radial ports 'i o'. threaded engagement With a fl n at extending through the piston above the upperthe; pp end of e Cy l mostpiston ring and below the top of the piston. The intake p of Compressor is indicated These port's are preferably located in the plane at -2 and extends through the Wall of the y 40 of the axis of the wrist pin so as notto bema der 5. It;is' soi located as to communicate with 40' terially aitectedby wear of the piston'or cylinder. the middle or web portion of atrunk pi ton corn- While it isv impossible to state positively the prisihghn pp 'i d 23 d a wer head 24 principle of operation of these ports, careful tests Connected by a web structure 25. The upp d of compressors embodying the invention, show 3' p d d' Wi metallic piston rings 6, of 5 that the leakage through the ports when the whichthree: are illustrated. The lower head 24 45., compressor is in operation, is negligible, but be-' is provided with" oil rings 21 and 28, the ring comes sufficient to relieve'the pressure in the. Z81 being ofthe. slotted oil draining type. The working space of the compressor Wheneverthe head 241is immediately below the piston pin or compressor is at rest. a w-rist pin '29 to-whi'ch the connecting rod 3| is A possible explanation of this action isthefact connected. The rod 31 is connected to the usual thatwhen the comp r is in p y crank "(not shown) and forms a part of the oil film is maintained between thepiston-an'd 'the means for reciprocating the piston. cylinder walls, and enough of this oil film is deintake valve is mounted on the upper livered to the unloading ports to preclude subface of the head 23 and comprises a flexible, stantial flow through the ports. On the other valve disk 32, similar to the disk l3 and coacting with ribs 33 and 34 similar to the ribs l4 and IS. The suction ports 35 are located between the ribs 33 and 34. The disk32 is held to the head 23 by means of the screw 36.

The parts so far described conform generally to known construction and no novelty is claimed for these parts in the present application. They are illustrated as typical of compressor construction and are chosen for illustration merely because the construction is standard for one type of compressor manufactured by applicant's assignee.

A short distance below the upper marginof the head 23 and a short distance above the upper piston ring 26 are unloading ports 31 forming the subject matter of the present invention. As illustrated two such unloading ports are used extending laterally through the head 23 with their axes in a plane common to the axis of the wrist pin 29 and the axis of cylinder This location is chosen because at such points the cylinder and piston are subject to the minimum wear.

While the location of the ports in'the plane defined is preferred, the invention is not limited strictly in this respect. For example, if more than two ports are used they can not be located strictly in this plane, but it is considered better practice to locate them as'close to this plane as possible. a 1 I Generally stated, it is desirable thatthe ports 31 be of small diameter because the closing effect of oil is more pronounced with small ports than with large ones. Consequently, in some cases where considerable unloading capacity is necessary, it may prove desirable to use more than the two ports illustrated. Furthermore, the size of these portsissomewhat exaggerated in the drawing for the purpose of making them clearly visible.

Practical tests have shown that when the pis-" ton head 23 is reciprocating, that is, when the compressor is in operation, the leakage through the ports 31 is so small as to be negligible, but when the piston comes to rest, and particularly if it be at rest under conditions in which there is a substantial pressure in the working space between the topof the piston head 23 and head I, the ports will function to dissipate that pressure to the suction side of the head '23' and thus unload the compressor. I a

From the standpoints of maintenance, manufacture and certainty of operation, the invention has outstanding advantages. Since there are no moving parts, there is nothing to maintain and no possibility of a failure to function. The application of the invention involves merely the drilling of a few small ports, so that the invention can be inexpensively applied to existing compressors, as well as to new equipment. The ability to use successfully a motor only large enough to carry the running load offered by the compressor, results in a substantial savingin the first cost of the plant.

7 While it is not necessary that theunloading ports 31 be strictly radial, it is considered desirable that they be so. Further, it is believed that there is some operative coaction between these radial ports and the rings 26, the rings serving to distribute and control the oil film, which is believed to exercise at least a partial sealing action on the ports 37 while the compressor is in operation. 7

While the suction and discharge valve mechanism has been described in considerable detail, this is merely for the purpose of illustrating one practical embodiment of the invention, and implies no necessary limitation of the use of the invention with any particular valve or type of valve.

What is claimed is,

1. The combination of a compressor of the type comprising a cylinder and a reciprocating piston; and at least one unloading port of restricted size leading from a space at relatively low pressure through the peripheral walls of the piston to the area of contact between piston and cylinder.

2. The combination of a compressor of the type comprising a cylinder and a reciprocating piston having packing rings; and at least one unloading port of restricted size leading from a space at relatively low pressure through the peripheral wall of the piston to the area of contact between the cylinder and piston at a point between the working space in the cylinder and the ring nearest thereto.

' 3. The combination of a compressor of the type comprising a cylinder and a reciprocating piston having a wrist pin; and at leastone unloading port of restricted size leading frorn a space'at relatively low pressure through the peripheral wall of the piston to the area of contact between piston and cylinder, said port being located substantially in a plane common to the axes of the cylinder and wrist pin.

4. The combination of a compressor of the type comprising a cylinder and a reciprocating piston having packing rings and a'wrist pin; and

at least one unloading port of' restricted-size leading from a space at relatively low pressure through the peripheral wall of the piston to the area of contact between the cylinder and piston, at a point between the working space in the cylinder and the ring nearest thereto, said port being located substantially in a plane common to the axes of said cylinder and wrist pin.

5. In a compressor, the combination of a cyltion space through the periphery of the piston to the area'of contact of the piston and cylinder between said rings and said compression space. a '7. The combination defined in claim 1, in which said space at relatively low pressure is in communication with the suction connection of the compressor.

. 8. The combination defined inclaim 2, in which said space at relatively low pressure is in communication with the suction connection of the compressor.

. 9. The combination defined in claim 3, in which said space at relatively low pressure is in communication with thesuction connection of the compressor.

10. The combination defined in claim 4, in which said space at relatively low pressure isin communication with the suction connection of' the compressor.

- FRENCH E. DENNISON'. 

